Islamic State of Iraq and the Levant's (Isil) Egyptian affiliate has claimed responsibility for a wave of attacks in the northern Sinai Peninsula yesterday that killed dozens of soldiers.

In a statement, the extremist group, known as Sinai Province, claimed it had launched 15 separate attacks, including two car bombs, in the towns of Al-Arish and Sheikh Zuwayid, near Egypt's border with Gaza and Israel.

Health officials said ambulances could not access the scene of the attacks because of heavy fighting, pitting jihadists on the ground against military helicopters. The jihadists had reportedly laid mines along nearby roads in an attempt to prevent the arrival of reinforcements that might stop the bloodshed.

By afternoon, security officials said the death toll had reached 70, with dozens of soldiers injured, marking one of the army's worst losses in its four-year-long campaign against Isil and its al-Qa'ida-inspired forerunner. The army said five checkpoints were attacked by about 70 militants and that soldiers had destroyed three landcruisers fitted with anti-aircraft guns.

North Sinai is the epicentre of a jihadist insurgency that has sporadically reared its head in the capital, Cairo. Hundreds of policemen and soldiers have been killed in attacks since the army toppled Islamist president Mohammed Morsi after mass protests against his rule in 2013.

Although Sinai Province has repeatedly proven its ability to conduct coordinated attacks on multiple targets, experts saw yesterday's assault as a move towards tactics favoured by Isil in Syria and Iraq.

"The fact that militants have not yet run - and seem to be set up for a long fight - suggests a change in strategy toward an Isil-like 'holding' of territory," said Zack Gold, visiting fellow at the Institute for National Security Studies in Tel Aviv. The move on a densely populated urban area, while unlikely to be successful, marked a departure from the group's previous attempts to minimise civilian casualties, Mr Gold added.

Sinai-based militants have exploited long-held grievances in the impoverished north of the peninsula, where the mainly Bedouin population has complained of neglect by Cairo authorities.

Abdel Fattah al-Sisi, the Egyptian president, has promised to speed up the trial of terrorism suspects, following the assassination of prosecutor general Hisham Barakat in Cairo on Monday.